1. Field of the Invention
The present invention relates to a process for the preparation of leatherlike sheet materials. More particularly, the present invention is concerned with a process for manufacturing leatherlike sheet materials from hollow composite fibers of a type which generates extra fine fibers, each hollow composite fiber composed of polyester or polyamide segments and polystyrene segments.
2. Description of the Prior Art
Heretofore, it has been known to produce leatherlike sheet materials using extra fine fibers. U.S. Pat. No. 4,051,287, issued on Sept. 27, 1977 to Hayashi et al and U.S. Patent Application Ser. No. 799,818, filed on May 23, 1977, now U.S. Pat. No. 4,109,038 by Ozaki et al disclose a suede-like woven or knitted fabric (a leatherlike sheet material) which was produced by applying an elastic polymer to a raised woven or knitted fabric comprising extra fine fibers obtained from hollow composite fibers, the hollow composite fiber being composed of at least four alternately arranged segments of fiber-forming polyester and fiber-forming polyamide which are mutually adhered side-by-side encompassing a hollow space and which extend along the longitudinal axis of the fiber to form a tubular body. This hollow composite fiber has the advantages that the segments of the hollow composite fiber are readily separable by mechanical action to form extra fine fibers and all the segments are usable as extra fine fibers. The obtained extra fine fibers, however, must be dyed by a very complicated process, because they consist of two polymers having properties different from each other.
U.S. Pat. No. 3,865,678, issued on Feb. 11, 1975 to Okamoto et al, discloses a suede-like raised woven fabric (a leatherlike sheet material) which was produced by applying an elastic polymer to a raised woven fabric comprising extra fine fibers obtained from islands-in-sea type composite fibers. The islands-in-sea type composite fiber can be converted into a bundle of the island component fibers (extra fine fibers) by removing the sea component from the composite fiber. However, the islands-in-sea type composite fiber has the disadvantages that a spinneret having a complicated structure must be employed in the manufacturing process of the islands-in-sea type composite fiber and further the process control is very difficult.
Japanese Patent Application Laid-Open No. 48402/76, Takemura et al, published on Apr. 26, 1976 discloses a hollow composite fiber which is divisible into fine fibers, and a leatherlike sheet material which is obtained by applying a polyurethane to a non-woven fabric formed with the hollow composite fibers. As for a divisible polymer combination, the Japanese Patent Application discloses the combination of polyamide and polyethylene terephthalate, polyethylene terephthalate and polystyrene, and also polyamide and polystyrene. However, the Japanese Patent Application neither teaches the denier of the fine fibers nor suggests the structure of the hollow composite fiber composed of polyester or polyamide and polystyrene segments.
According to the experiments conducted by the present inventors, it was very difficult to produce a hollow composite fiber having good properties composed of polyester or polyamide and polystyrene segments. In manufacturing a hollow composite fiber composed of alternately arranged segments of polyester or polyamide and polystyrene which are mutually adhered side-by-side and encompass a hollow space, the drawing operation of the melt-spun hollow composite fiber was very difficult, because the adhesive force between the segments of different polymers was poor and the physical properties of the segments of different polymers greatly differed from each other, and accordingly it was very difficult to obtain the hollow composite fiber suited for commercial use.